JEE PYQ: Surface Chemistry Question 27
Question 27 - 2019 (09 Apr Shift 2)
Type: MCQ
10 mL of 1 mM surfactant solution forms a monolayer covering $0.24$ cm$^2$ on a polar substrate. If the polar head is approximated as a cube, what is its edge length?
(a) 1.0 pm
(b) 2.0 pm
(c) 0.1 nm
(d) 2.0 nm
Show Answer
Answer: (a)
Solution
No. of surfactant molecules $= 6 \times 10^{23} \times \frac{10}{1000} \times 10^{-3} = 6 \times 10^{18}$
Let edge length $= a$ cm
Total surface area of surfactant $= 6 \times 10^{18} \times a^2 = 0.24$ cm$^2$
$a^2 = \frac{0.24}{6 \times 10^{18}} = 0.04 \times 10^{-18} = 4 \times 10^{-20}$
$a = 2 \times 10^{-10}$ cm $= 2$ pm
BETA
